Current technologies utilized for gaseous hydrogen storage are limited by the low-volume storage gas density even at very high pressures, such as pressures in the range of 5,000 to 10,000 psi. The energy density by volume of the gaseous hydrogen is less than that of a gasoline energy density. Use of hydrogen as an alternate fuel is limited due to this lower energy density. Cryogenic storage of hydrogen at temperatures of around 20 K may improve the volumetric energy density compared to gaseous storage, but is still less than that for a given amount of energy when compared to gasoline. Additionally, production of liquid hydrogen is energy intensive and requires special considerations due to the low temperature storage to avoid hydrogen boil off and other limitations of liquefied hydrogen.
Chemical storage of hydrogen in a solid, such as borohydride, allows for hydrogen release when heated or mixed with water. However, formation of solid byproducts or release of hydrogen at very high temperatures, usually exceeding the melting point of the borohydride, limit the use of borohydrides. Additionally, borohydrides are not typically able to be rehydrided after hydrogen release.
There is therefore a need in the art for an improved hydrogen storage material that releases hydrogen at lower temperatures and is able to be rehydrided after release of the hydrogen.